Once the seat of Viking raiders and later a major north European power, Denmark has evolved into a modern, prosperous nation that is participating in the general political and economic integration of Europe. It joined NATO in 1949 and the EEC (now the EU) in 1973. However, the country has opted out of certain elements of the EU's Maastricht Treaty, including the European Economic and Monetary Union, European defense cooperation, and issues concerning certain justice and home affairs.